The present invention relates to a power window which is used in a vehicle such as an automobile to effect the operation of opening and closing a window by a driving source such as a motor, and more particularly to a safety device which performs a safety controlling operation by detecting a state in which a passenger's hand, head, or the like is nipped between window glass and a sash.
In a power window, since the window glass is generally made to undergo opening and closing operations by a motor or the like, an accident can occur in which a passenger's hand, head, or the like is nipped between the window glass and the sash. For this reason, safety devices have been conventionally proposed for preventing an accident by detecting the state of a foreign object being nipped between the window glass and the sash, and by such as stopping the operation of opening or closing the window glass or effecting the operation of opening the window glass at that time. As such window safety devices proposed by the present applicant, various devices have been proposed including Unexamined Japanese Patent Application Publication No. Hei. 5-321530. As a safety device of this type, the motor for driving the window glass is furnished with a pulse signal oscillator comprising a Hall element, and a safety control region is determined by detecting the absolute velocity and relative velocity of the closing operation of the window glass by a detecting means on the basis of this pulse signal and by detecting the opening or closing direction by the detecting means. During the closing operation, the nipping of a foreign object is detected from at least one detection result of the absolute velocity and the relative velocity. Then, when the nipping of the foreign object is detected, safety control is effected for forcibly operating the window glass in the opening direction so as to release the foreign object from nipping by the window glass and the sash.
According to such a safety-control-region determining technique, however, since an error occurs in the determination of the safety control region due to the miscounting of the pulse signal and the like, a window-glass-position detecting mechanism such as a limit switch is newly required in the vicinity of the upper limit of the window glass. Further, as proposed in, for example, Unexamined Japanese Patent Application Publication No. Hei. 8-303113, this window-glass-position detecting mechanism requires an automatic position adjusting mechanism to omit the mounting-position adjusting operation in the assembling process in an automobile plant, so that the structure becomes complex, constituting a cause for leading to higher cost.
Accordingly, it is conceivable to determine positions for opening and closing the window by a position sensor and detect the state of the opening and closing operation of the window by means of an output from the position sensor. In this case, as the position sensor, if, for example, a potentiosensor is arranged along a rail along which the window is made to undergo the opening and closing operations, since the resistance value of the potentiosensor varies depending on the opening and closing positions of the window, it is possible to detect the opening and closing positions of the window. This arrangement, however, requires a potentiosensor of a length extending over the entire stroke of the opening and closing operation of the window, so that the structure of the vehicle window becomes complex, and it is difficult to overcome the aforementioned higher cost.